Stabilization of long bones of the human body, following fractures, malformations or similar pathologic situations is known to be attained by using well-known devices such as intramedullary nails, consisting of more or less curved hollow or solid metal rods, which are fitted into the intramedullary cavity of the bones to be stabilized and are anchored to the stumps or parts to be stabilized by transverse-pins or screws, typically in the distal and proximal region of the limb. Once the fracture has been stabilized and fixed, the pins are removed and the nail is extracted from the medullary canal.
One problem associated to such treatment, in addition to the invasiveness of the implantation procedure, is the establishment of infection foci, which may locally develop due to the incompatibility of metal with the spongy medullary tissue and due to the bacteria that normally come in contact with the implantation site.
In order to minimize such drawbacks, it is highly recommended that the implantation of the above devices occurs in wholly sterile conditions, and that the relevant part is treated with substances adapted to prevent and/or treat such infections.
In an attempt to at least partly obviate the above drawbacks, solutions have been developed to allow in situ application of the above substances, alone or added to bone cement.
The U.S. Pat. No. 4,863,444 discloses a carrier shaped like a stick through which an antibiotic could be distributed. The stick, due to its elongated configuration, can be inserted into the channel provided through the skin and the soft tissues for the accommodation of an external fixture comprising a screw or a nail introduced into the bone.
A solution is known in which a cover for the stabilizer device is made by using molds at the factory or directly at the surgical site immediately before implantation of such device.
This solution also has several apparent drawbacks.
First, it is a substantially manual solution, which requires special skills from the operator, who has to be properly trained therefor. Such an operation further involves many processing scraps, thereby causing a high material waste and an increase of the overall processing costs.
The thus covered device is also exposed for a sufficiently long time to air and to contact with foreign material, which involves a high risk of attack by bacteria and contaminants.
Furthermore, the covered device which comes out of the mold will exhibit many burrs along its longitudinal extension, which will have to be removed for proper positioning, thereby involving longer implantation times and consequent discomfort for the patient.
A further aspect of the invention relates to the need of temporarily replacing an intramedullary nail for one of several different reasons, such as recidivation or dislocation of the implant, normally followed by surgical site infections.
In these situations, the existing intramedullary nail has to be removed and the implant site has to be treated before insertion of the new nail. In the meantime, the geometry of the site shall be maintained unchanged, to prevent shortening and deformation of tissues, by providing a spacer device which can also prevent and/or treat the infections due to the old and new implant.